Methanol-powered artificial muscles have been created by researchers aiming to create battery-free robotic limbs and prosthetics.

"One day you could find yourself sitting in a bar next to a humanoid robot, who is taking a shot of vodka to give himself the energy to go to work," jokes Ray Baughman, a nanotechnologist at the University of Texas at Dallas, US.

"The most athletic robots around today are chained to a power source, so they can't move about freely," he explains. In an effort to remove the robots from their battery-shackles, Baughman and colleagues have designed two types of artificial muscle that also act as fuel cells – converting chemical energy to mechanical movement.

The first type of muscle is made from a nickel-titanium shape-memory wire coated in a platinum catalyst. When fumes of methanol, hydrogen and oxygen pass over the platinum coating, they react, releasing heat that warms the wire, making it contract. When the flow of fuel is stopped, the wire expands and returns to its original length. The wire muscle can generate 100 times the force of a natural muscle of the same size, says Baughman.

Energy saver
The team's second artificial muscle is made from sheets of carbon nanotubes, coated in a catalyst. It is not yet as powerful as the wire muscle, but could potentially overtake it, he says.

As the fuel reacts with oxygen above the surface of the nanotube sheet, it releases a charge that make the sheet expand. The big advantage of the nanotube muscle is that it can also act as a capacitor, storing up electric energy it does not immediately need for later use, Baughman explains.

The team are now working out exactly how to control the flow of fuel in practical prosthetic applications. Baughman believes that people with limited finger or arm mobility could control an artificial muscle using very slight movements to open and shut a valve to release the fuel. A second challenge for the group is ensuring that the muscles do not overheat as they contract, adds Baughman.

“It is very clever that the muscle itself is the fuel cell,” says Siegmar Roth, an artificial muscle expert at the Max Planck Institute in Stuttgart, Germany. “This will be very good for medical applications because you can’t put high voltages into humans, but these work on low voltages.”

I think there's something more in that too, the drink-loving Bender does take on a new meaning considered alongside fuels like methanol and ethanol.

Don't LCDs use rapid minuscle heat-changes to display the colours on monitors, sounds like the kind of hyper-sensitivity needed for the prosthetics. I'd also go for two thumbs, one on each side, and four index fingers where hands are concerned.